In the parlance of the transmission designer, a synchronization piece is also termed a pressure piece or synchronization pressure piece.
As presented in detail at the VDI conference “Getriebe in Fahrzeugen 2006” (“Transmission in Vehicles 2006”) and set out on pages 171-192 of the corresponding conference proceedings, published by VDI-Wissenforum, ISBN 3-18-091943-4, a KYOWA HIGH PERFORMANCE SYNCHRONIZER (KHS) is now known in the specialist domain. This synchronizer, as a H element, is capable of performing a locking synchronization according to the servo synchronization principle. The principle of servo synchronization is set out in greater detail in, for example, U.S. Pat. No. 3,548,983 and, in the same document family, the German document DE 1 924 724 C (published on Nov. 20, 1969, patent holder Nissan Motor Co.), the full content of the explanations relating to servo synchronization in that publication having been incorporated by reference herein.
A synchronization system is termed a servo synchronization system if the energy from the torque of the gear wheels that are capable of rotation relative to one another is used to facilitate the synchronization operation. It would also be advantageous, in the case of a servo synchronization system, to reduce the force required for unblocking between the sliding sleeve and the synchronizer ring. Normally, even in the case of servo synchronization systems, the unblocking force is to some extent greater than the synchronizing force to be applied through the shifting operation. The shifting force applied to the synchronization system via the shift lever of the gearshift linkage is amplified in the case of a servo synchronization system.
Further ways of advantageously utilizing the synchronization moment in the case of a transmission synchronization system are to be found in, for example, U.S. Pat. Nos. 4,573,371, 4,674,614 and 5,924,535. U.S. Pat. No. 5,924,535 and its cross-references refer to the use of the synchronization moment as “self-energizing” synchronization with use of the ramp friction. The full content of the descriptions relating to the servo synchronization according to the latter document has been included herein by reference. It is to be emphasized that in some cases the documents refer to ramp friction or self-energizing use of the meshing operation, when what is meant thereby is servo synchronization.
Known from DE 1 650 814 A is a ball-type pressure piece for any synchronizer ring composed of three balls arranged in succession. The pressure piece is located beneath an expanding circular-ring segment. A radial servo synchronization principle is realized by means of the expanding effect of the circular segment, in particular its two ends.
The wobbling of two opposing synchronizer rings can be prevented (see, for example, DE 10 2004 036 507 B3 and DE 24 31 324 A) in that a pressure-piece type element extends from one synchronizer ring to the next synchronizer ring, and engages in the two mutually facing synchronizer rings. The two synchronizer rings are thereby braced in relation to each other.
Compared with the earlier synchronization pressure pieces, the known H pressure piece is distinguished by its simplicity. It can be integrated into known synchronization systems without any need for substantial modification of the other parts. This means that the resource requirement for modification is limited in the case of introduction of an H pressure piece, and customer clearance is more easily obtainable. A disadvantage is the necessity of a repeat, separate hardening of the ends of the H piece during production. In addition, in order for the ends to withstand the forces that occur, their walls must be of a certain minimum thickness. Owing to its shape, an H piece has a minimum width. The hub is round, with the result that, owing to its curvature, the H piece exerts a certain notch effect. As in the case of a conventional synchronization system, the unblocking force is not reduced.